1. Field of the Invention
This invention is directed to worm and gear drives, and more particularly to a structure providing minimum backlash, and/or rigid locking between the worm and gear upon completion of driving.
2. Background Art
Worm and gear drives are well known in the art. Such drives have many uses, including driving pan and tilt housings for TV cameras and for radio or micro-wave equipment. In such uses, it is desirable, and often crucial, that the clearance between the worm and gear be minimized to eliminate any backlash or looseness which would cause a wobble in the supported equipment. Such a wobble is highly undesirable when, for example, attempting to view the picture on a TV camera taken through a telephoto lens.
Heretofore, the worm, its shaft and its bearings have been mounted in a carrier and that carrier has been adjusted radially to the gear during assembly to move the worm and gear together. In practice, there is always some eccentricity in the worm teeth and the gear teeth, and therefore, in view of the inability to form perfect parts, a running clearance has been maintained between the teeth to avoid jamming. Further, due to the common and unavoidable eccentricities and other variations in the worm and gear, when the carrier has been adjusted for a minimum fit, of necessity it has been positioned to provide that minimum fit when the high sides of the worm and gear are together. At all other positions there is a greater spacing between the teeth than at the minimum fit position leading to clearances allowing undesirable looseness, wobble, vibration and the like.
The carriers used to arrange the worm for minimum fit have been relatively difficult to adjust to provide minimum fit between the worm and gear. Even when the worm is properly mounted to provide a minimum fit, that backlash and looseness is minimized in only one position of the worm and gear. There is in fact a backlash and looseness between the worm and gear in every other position, which looseness can result in a wobble in the supported equipment and/or other undesirable effects in the output shaft.
The present invention is directed toward overcoming one or more of the problems as set forth above.